feat: Passwordless cross-device authentication

- Arkitektur: docs/auth/passwordless-architecture.md
- Backend: iom/quixzoom-auth-service/ (FastAPI + Redis)
- Webb: quixzoom-market-pages/se/login/ (QR-kod + polling)
- App: iom/quixzoom-app/src/features/auth/ (push + deep links)

Flöde: QR-kod → app-godkännande → webb-inloggad

landvex-admin-v2/node_modules/canvas/lib/pdfstream.js

@@ -0,0 +1,35 @@
+'use strict'
+
+/*!
+ * Canvas - PDFStream
+ */
+
+const { Readable } = require('stream')
+function noop () {}
+
+class PDFStream extends Readable {
+  constructor (canvas, options) {
+    super()
+
+    this.canvas = canvas
+    this.options = options
+  }
+
+  _read () {
+    // For now we're not controlling the c++ code's data emission, so we only
+    // call canvas.streamPDFSync once and let it emit data at will.
+    this._read = noop
+
+    this.canvas.streamPDFSync((err, chunk, len) => {
+      if (err) {
+        this.emit('error', err)
+      } else if (len) {
+        this.push(chunk)
+      } else {
+        this.push(null)
+      }
+    }, this.options)
+  }
+}
+
+module.exports = PDFStream